1. Field of the Invention
The invention relates to techniques for performing vascular and intestinal occlusion and, more particularly, to a clamp for such occlusion.
2. Description of the Prior Art
The body contains many conduits that accommodate a flow of fluids or semi-solids. Such conduits include the intestines and blood vessels, both veins and arteries. Many surgical procedures require that the flow in such conduits be reduced or halted (“occlusion”) while surgical procedures such as anastomosis are performed. For convenience, any portion of the intestinal tract, any vascular member, or any other portion of the body that transports or convey fluids, semi-solids, or other material will be referred to herein as a “conduit” or “conduits.”
Occlusion in conduits typically is accomplished by devices commonly referred to as clamps or clips. In general, these devices have opposing jaws that are adapted to extend over the conduit and to pinch the walls of the conduit against themselves in order to inhibit or stop flow through the conduit. The jaws commonly associated with clamps are relatively long and are operable by scissor-type handles which provide leverage for the jaws. Representative clamps of this type are shown in U.S. Pat. Nos. 5,019,092 and 5,447,515, the disclosures of which are incorporated herein by reference. Clamps commonly are used to occlude larger conduits such as the intestines. By comparison, the jaws of clips are relatively small and are biased by a spring commonly used to occlude smaller conduits such as blood vessels. As used herein, the term “clamp” will refer not only to clips and clamps, but also to other types of occlusion devices which have opposing jaws.
Conduits typically have a relatively smooth outer surface which often is wetted by body fluids such as blood. Attempts to occlude such conduits by pinching their walls must meet several objectives. The primary objective is to accomplish the occlusion, but of no less importance is a second objective, which is to maintain the clamp in place. Another objective is to occlude the conduit without causing tissue damage or necrosis, sometimes attributed to localized pressure or stress concentrations.
Traction is related to the resistance of the clamp to movement relative to the tissue. Theoretically, traction is equivalent to the product of the coefficient of friction, which is dependent upon the nature of the contacting surfaces, and the normal or clamping force. In the past, attempts have been made to increase this clamping force in order to increase the traction. Unfortunately, squeezing a conduit with a greater force tends to traumatize the tissue and in the case of blood vessels, destroy the intimal lining which cannot be regenerated. As a result, it is desirable to have only sufficient clamping force to achieve the first objective, that is, the occlusion of the conduit. Increasing the clamping force to achieve the second objective, that is, to increase traction, generally is not a suitable alternative.
Attempts have been made to increase the coefficient of friction in order to enhance the traction of the clamp relative to the conduit. This has been complicated by the wetness of the tissue surface of the conduit. U.S. Pat. No. 3,746,002 discloses an atraumatic surgical clamp having a plurality of pin members which extend though a resilient pad and which engage the tissue when the pad is compressed. Since the pins stick into the tissue, this produces a highly traumatic effect in most cases. Less aggressive attempts to increase the coefficient of friction have not always been sufficient to maintain the clamp in place, even after the conduit has been occluded.
Resilient pads, commonly referred to as inserts, have been provided for attachment to the inner surfaces of the opposing jaws. These inserts typically have a tissue-contacting surface which faces the opposing jaw, as well as a pair of side-surfaces which extend laterally of the insert. The inserts have been formed of resilient foam, in some cases with irregular surfaces. Other inserts have included fibers in the nature of toothbrush bristles to increase traction. Such inserts have experienced problems in either successfully occluding the conduit or in maintaining proper traction thereon. Examples of these various types of devices in question are shown in U.S. Pat. Nos. 4,106,508; 4,708,140; 4,98,355; and 6,579,304, the disclosures of which are incorporated herein by reference.
Unfortunately, although existing externally applied devices and techniques appear to offer a relatively simple and effective approach to the problem of occluding a conduit, a significant problem that remains is that of tissue damage, possibly even necrosis. If the compressive force that is applied to the conduit is too great, or if compression is localized in some areas and not others, the device either could cause undesired cell destruction or it could fail to perform its occlusion function properly.
Desirably, an externally applied exclusion device for a conduit would be available that would be easy to apply and remove. Any such device preferably would apply the proper amount of compressive force to occlude the conduit while avoiding any stress concentrations that would lead to undesired tissue damage or necrosis. Moreover, any such device hopefully would avoid punctures that would lead to difficult-to-control bleeding. Yet additionally, any such device would have adequate traction to maintain the device in its proper position on the conduit.